SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
            TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO
                                  RULE 13d-2(a)

                          Catalyst Semiconductor, Inc.
                                (Name of Issuer)

                                  Common Shares
                         (Title of Class of Securities)

                                   148881-10-5
                                 (CUSIP Number)

                              Attn: Paul B. Goucher
                       J. & W. Seligman & Co. Incorporated
                                 100 Park Avenue
                               New York, NY 10017
                                 (212) 850-1864
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                  June 15, 2007
             (Date of Event Which Requires Filing of This Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the subject of this  Schedule  13D, and is filing this
schedule  because of Rule  13d-1(e),  13d-1(f) or 13d-1(g),  check the following
box. |_|

Note:  Schedules  filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See Rule 13d-7 for other parties
to whom copies are to be sent.


                         (Continued on following pages)


(1) The  remainder  of this  cover  page  shall be  filled  out for a  reporting
person's  initial  filing on this  form with  respect  to the  subject  class of
securities,  and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purposes of Section 18 of the  Securities  Exchange Act of
1934 or  otherwise  subject to the  liabilities  of that  section of the Act but
shall be subject to all other provisions of the Act (however, see the Notes).



------------------------
CUSIP No. 148881-10-5                  13D
------------------------
================================================================================
    1.  NAME OF REPORTING PERSON

        J. & W. Seligman & Co. Incorporated

        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON (ENTITIES ONLY)

        13-3043476
--------------------------------------------------------------------------------
    2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) |_|
                                                                         (b) |_|
--------------------------------------------------------------------------------
    3.  SEC USE ONLY

--------------------------------------------------------------------------------
    4.  SOURCE OF FUNDS

        AF
--------------------------------------------------------------------------------
    5.  CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
        ITEMS 2(d) OR 2(e)
                                                                             |_|
--------------------------------------------------------------------------------
    6.  CITIZENSHIP OR PLACE OF ORGANIZATION

        Delaware
--------------------------------------------------------------------------------
                            7. SOLE VOTING POWER

                               0
                          ------------------------------------------------------
 NUMBER OF                  8. SHARED VOTING POWER
   SHARES
BENEFICIALLY                   855,666
  OWNED BY                ------------------------------------------------------
    EACH                    9. SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                    0
                          ------------------------------------------------------
                           10. SHARED DISPOSITIVE POWER

                               855,666
--------------------------------------------------------------------------------
    11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

        855,666
--------------------------------------------------------------------------------
    12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

                                                                             |_|
--------------------------------------------------------------------------------
    13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

        5.2%
--------------------------------------------------------------------------------
    14. TYPE OF REPORTING PERSON

        IA, CO
================================================================================


                                       2


---------------------------------
CUSIP No. 148881-10-5                  13D
---------------------------------
================================================================================
    1.  NAME OF REPORTING PERSON

        Seligman Spectrum Focus (Master) Fund

        I.R.S. IDENTIFICATION NOS. OF ABOVE PERSON (ENTITIES ONLY)

        98-0498128
--------------------------------------------------------------------------------
    2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) |_|
                                                                         (b) |_|
--------------------------------------------------------------------------------
    3.  SEC USE ONLY

--------------------------------------------------------------------------------
    4.  SOURCE OF FUNDS

        WC
--------------------------------------------------------------------------------
    5.  CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
        ITEMS 2(d) OR 2(e)
                                                                             |_|
--------------------------------------------------------------------------------
    6.  CITIZENSHIP OR PLACE OF ORGANIZATION

        Cayman Islands
--------------------------------------------------------------------------------
                            7. SOLE VOTING POWER

                               0
                          ------------------------------------------------------
 NUMBER OF                  8. SHARED VOTING POWER
   SHARES
BENEFICIALLY                   855,666
  OWNED BY                ------------------------------------------------------
    EACH                    9. SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                    0
                          ------------------------------------------------------
                           10. SHARED DISPOSITIVE POWER

                               855,666
--------------------------------------------------------------------------------
    11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

        855,666
--------------------------------------------------------------------------------
    12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

                                                                             |_|
--------------------------------------------------------------------------------
    13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

        5.2%
--------------------------------------------------------------------------------
    14. TYPE OF REPORTING PERSON

        CO
================================================================================


                                       3


---------------------------------
CUSIP No. 148881-10-5                                    13D
---------------------------------
================================================================================
    1.  NAME OF REPORTING PERSON

        William C. Morris
--------------------------------------------------------------------------------
    2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) |_|
                                                                         (b) |_|
--------------------------------------------------------------------------------
    3.  SEC USE ONLY

--------------------------------------------------------------------------------
    4.  SOURCE OF FUNDS

        AF
--------------------------------------------------------------------------------
    5.  CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
        ITEMS 2(d) OR 2(e)
                                                                             |_|
--------------------------------------------------------------------------------
    6.  CITIZENSHIP OR PLACE OF ORGANIZATION

        USA
--------------------------------------------------------------------------------
                            7. SOLE VOTING POWER

                               0
                          ------------------------------------------------------
 NUMBER OF                  8. SHARED VOTING POWER
   SHARES
BENEFICIALLY                   855,666
  OWNED BY                ------------------------------------------------------
    EACH                    9. SOLE DISPOSITIVE POWER
 REPORTING
PERSON WITH                    0
                          ------------------------------------------------------
                           10. SHARED DISPOSITIVE POWER

                               855,666
--------------------------------------------------------------------------------
    11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

        855,666
--------------------------------------------------------------------------------
    12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

                                                                             |_|
--------------------------------------------------------------------------------
    13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

        5.2%
--------------------------------------------------------------------------------
    14. TYPE OF REPORTING PERSON

        IN
================================================================================


                                       4


                                  SCHEDULE 13D


Item 1. Security and Issuer.

This  statement on Schedule 13D relates to the common  stock,  no par value (the
"Common Shares"), of Catalyst  Semiconductor,  Inc., a Delaware corporation (the
"Issuer").  The Issuer's  principal  executive office is 2975 Stender Way, Santa
Clara, CA 94054.

Item 2. Identity and Background.

(a)-(c)  This  statement  is  filed  on  behalf  of  J.  &  W.  Seligman  &  Co.
Incorporated,  a Delaware corporation ("JWS"),  Seligman Spectrum Focus (Master)
Fund, a Cayman Islands  corporation  ("SSF") and William C. Morris,  controlling
shareholder  of JWS  ("Morris",  and together  with JWS and SSF, the  "Reporting
Persons").  The Reporting Persons are filing jointly and the agreement among the
Reporting  Persons  to  file  jointly  is  attached  hereto  as  Exhibit  1  and
incorporated  herein by reference.  The address of the principal business office
of JWS,  Morris  and each  director  and  executive  officer  of JWS is 100 Park
Avenue,  New York,  NY 10017.  The  principal  address of SSF is P.O. Box 309GT,
Ugland House, South Church Street, George Town, Grand Cayman, Cayman Islands.

JWS is an investment  adviser and the name and present  principal  occupation or
employment  of each  director and executive  officer of JWS is  incorporated  by
reference to JWS's Form ADV (File No.  801-15798)  as filed with the  Securities
Exchange  Commission on May 8, 2007. Each director and executive  officer of JWS
is a citizen of the United States, except Rodney G. D. Smith who is a citizen of
Great Britain.

SSF is a foreign investment company.  The name, present principal  occupation or
employment and  citizenship  of each director of SSF are listed below.  SSF does
not have any  officers.  The business  address for each is 100 Park Avenue,  New
York, NY 10017



--------------------------------------------------------------------------------------------------------------
       Name of Directors of SSF                   Principal Occupation                    Citizenship
       ------------------------                   --------------------                    -----------
--------------------------------------------------------------------------------------------------------------
                                                                                    
John J. Guancione                        Managing Director of JWS                         USA
--------------------------------------------------------------------------------------------------------------
Richard M. Potocki                       Managing Director of Seligman
                                         Advisors, Inc.                                   USA
--------------------------------------------------------------------------------------------------------------
Rodney G .D. Smith                       Director and Managing Director of JWS            Great Britain
--------------------------------------------------------------------------------------------------------------
Brian T. Zino                            Director and President of JWS                    USA
--------------------------------------------------------------------------------------------------------------


Morris is the Chairman of JWS and, as the owner of a majority of the outstanding
voting  securities of JWS, may be deemed to beneficially own the shares reported
herein by JWS.

(d),(e)  During the last five years,  none of the Reporting  Persons and none of
the directors and executive officers of JWS and SSF have been (i) convicted in a
criminal  proceeding  (excluding traffic violations or similar  misdemeanors) or
(ii) a party to a civil  proceeding  of a  judicial  or  administrative  body of
competent jurisdiction and as a result of such proceeding was or is subject to a
judgment,  decree or final order enjoining future  violations of, or prohibiting
or mandating  activities subject to, federal or state securities laws or finding
any violation with respect to such laws.

(f) Morris is citizen of the United States of America.


                                       5


Item 3. Source and Amount of Funds or Other Consideration.

In acquiring the Common Shares reported herein, SSF expended  approximately $3.1
million (including commissions) of its working capital.

Item 4. Purpose of Transaction.

The Reporting Persons acquired the Common Shares  beneficially owned by them for
investment  purposes.  The Reporting  Persons expect to continually  monitor and
re-evaluate their investments in the Common Shares.

JWS believes that the Issuer's  business is profitable (on a non-GAAP basis) and
growing and that the Issuer's Common Shares are significantly undervalued. Based
upon the Issuer's enterprise value of $33.4 million(1)  (excluding  assets(2) of
$40.4  million),  the Common  Shares are  currently  trading at 0.4x Wall Street
estimates  for the  Issuer's  2008 fiscal year  revenue.  Excluding  cash,  cash
equivalents  and short-term  investments of $28.6  million,(2) the Common Shares
are currently trading at 0.6x Wall Street estimates for the Issuer's 2008 fiscal
year revenue.

In order to enhance shareholder value, JWS has recommended to the Issuer's Board
of  Directors  that the  Issuer  buyback  one to two  million  Common  Shares in
addition to the Common Shares that the Board has currently authorized the Issuer
to repurchase.  JWS believes that the Issuer can accommodate a repurchase of its
Common Shares at the recommended  level because it represents  approximately 15%
to  29%  of  the  Issuer's  available  cash,  cash  equivalents  and  short-term
investments of $28.6 million,(2) inclusive of an increase of $2.9 million during
its last fiscal  quarter.(3)  Additionally,  JWS  believes  that the Issuer will
continue to generate cash from operations.

As part of this continuing  process of monitoring their investment in the Common
Shares,  representatives  of the  Reporting  Persons  may from time to time hold
talks or  discussions  with,  write  letters to and  respond to  inquiries  from
various parties, including, without limitation, the Issuer's Board of Directors,
management or representatives, other shareholders and other persons or entities,
regarding the Issuer's affairs and strategic alternatives.

From time to time in the past,  representatives  of the  Reporting  Persons have
contacted members of the Issuer's  management and Board of Directors in order to
communicate  the  views of the  Reporting  Persons  as to how  best to  maximize
shareholder  value.  The initiatives that have been recommended by the Reporting
Persons for consideration by the Issuer's management and Board of Directors have
included  instituting  a share  buy-back  program,  marketing  securities of the
Issuer to investors and, ultimately, selling the Issuer to a strategic acquiror.
JWS is  considering  proposing a candidate for election to the Issuer's Board of
Directors  through a  submission  to the Board's  nominating  committee  and has
introduced, and may introduce in the future, candidates for consideration by the
Issuer for possible employment.

In  the  future,   the  Reporting  Persons  may  undertake  various  actions  or
initiatives  from time to time.  Subject to applicable  law and  regulation  and
depending upon various factors, including, the financial

-------------
(1) Based upon the Issuer's closing stock price of $4.20 as of June 21, 2007.

(2)  Reflects  $16.6  million  of cash and cash  equivalents,  $12.0  million of
short-term  investments  and $11.7 million of property and equipment,  net as of
April 29, 2007 as reported by the Issuer to the SEC in the  Issuer's  8-K filing
on June 14, 2007.

(3)  Based  upon  the  increase  of $2.9  million  in the  Issuer's  cash,  cash
equivalents  and short-term  investments  balance from January 28, 2007 to April
29, 2007,  as reported by the Issuer to the SEC in the  Issuer's  10-Q filing on
March 9, 2007 and 8-K filing on June 14, 2007, respectively.


                                       6


performance of the Issuer,  the  availability  and price of Common  Shares,  and
other general market and investment conditions, those actions may include:

o     acquiring  additional  Common  Shares,  through  open market  purchases or
      otherwise;

o     selling,  trading,  engaging in short selling of, hedging or entering into
      any similar  transactions with respect to the Common Shares,  through open
      market transactions or otherwise;

o     seeking representation on the Board of Directors of the Issuer;

o     making  recommendations  to the Board of Directors  and  management of the
      Issuer  concerning  various business  strategies,  mergers,  acquisitions,
      dispositions,   dividend  policy,   capital  structure,   share  buybacks,
      Certificate of Incorporation or Bylaws or other matters; or

o     taking  any  other  actions,   including   engaging  or  participating  in
      transactions,  that  could  have the  purpose  or  effect of  directly  or
      indirectly changing or influencing control of the Issuer.

Such actions may take place at any time and without prior notice. Conversely, it
is possible that none of the courses of action  described  above will be pursued
by any Reporting Person.

Item 5. Interest in Securities of the Issuer.

(a),  (b) Based upon the Issuer's  Quarterly  Report on Form 10-Q filed with the
Securities  and  Exchange  Commission  on March 9, 2007,  there were  16,411,187
Common  Shares  issued and  outstanding  as of  February  28,  2007.  As to each
Reporting  Person,  Items (7)-(11) and (13) of their  respective  cover page are
incorporated herein by reference.

JWS and Morris do not directly  own any shares of the Issuer.  The shares of the
Issuer reported herein are directly owned by SSF;  however,  SSF has engaged JWS
as its investment adviser with discretionary  authority to acquire,  dispose and
vote the shares of the Issuer. JWS, as investment adviser to SSF, and Morris, as
JWS's controlling shareholder, may be deemed to have the shared power to vote or
direct  the vote of (and the shared  power to dispose or direct the  disposition
of) the Common Shares reported herein.

(c) The trading dates,  number of Common Shares  purchased or sold and the price
per share for all  transactions  by the  Reporting  Persons in the Common Shares
within the last 60 days,  which were all  brokered  transactions,  are set forth
below:

                                             Number of Shares
Reporting Person                  Date      Purchased / (Sold)   Price Per Share
----------------               ----------   ------------------   ---------------

       SSF                     04/27/2007              200             3.75

       SSF                     04/30/2007              200             3.74

       SSF                     05/01/2007              300             3.75

       SSF                     05/10/2007            7,000             3.80

       SSF                     05/11/2007            4,000             3.80

       SSF                     05/11/2007           49,600             3.80

       SSF                     05/15/2007            7,300             3.74

       SSF                     05/24/2007           16,000             3.79

       SSF                     05/24/2007            2,447             3.80

       SSF                     05/25/2007              100             3.80



                                       7


       SSF                     05/29/2007           22,700             3.88

       SSF                     05/29/2007            7,977             3.82

       SSF                     05/30/2007            7,200             3.81

       SSF                     05/31/2007           13,676             3.80

       SSF                     06/01/2007              800             3.83

       SSF                     06/05/2007              600             3.85

       SSF                     06/08/2007           35,000             4.01

       SSF                     06/12/2007         6,800.00             4.05

       SSF                     06/13/2007        18,700.00             4.04

       SSF                     06/14/2007        36,750.00             4.03

       SSF                     06/15/2007        33,853.00             3.98

       SSF                     06/18/2007           26,900             4.00


(d) No person other than the  Reporting  Persons has the right to receive or the
power to direct the receipt of dividends  from, or the proceeds from the sale of
the Common Shares reported herein.

(e) Not applicable.

Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to
Securities of the Issuer.

Except for the matters  described  herein, no Reporting Person has any contract,
arrangement,  understanding or relationship  with any person with respect to any
securities of the Issuer.

Item 7.  Material to be Filed as Exhibits.

EXHIBIT     DOCUMENT
-------     --------

   1        Joint Filing Agreement by and among the Reporting Persons, dated
            June 22, 2007.

   2        Power of Attorney, granted by William C. Morris relating to Schedule
            13D and 13G filings, in favor of Frank J. Nasta, dated February 2,
            1998

   3        Certificate of Seligman Spectrum Focus (Master) Fund, dated June 15,
            2007


                                       8


                                    SIGNATURE

      After  reasonable  inquiry and to the best of my knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.


Dated:  June 22, 2007


                              J. & W. SELIGMAN & CO. INCORPORATED


                              By /s/ Thomas G. Rose
                                --------------------------------
                              Name:   Thomas G. Rose
                              Title:  CFO


                              SELIGMAN SPECTRUM FOCUS (MASTER) FUND


                              By /s/ Lawrence P. Vogel
                                --------------------------------
                              Name:   Lawrence P. Vogel
                              Title:  Authorized Person


                              WILLIAM C. MORRIS
                                   By Frank J. Nasta,
                                   as attorney-in-fact for William C. Morris

                              /s/ Frank J. Nasta
                              ----------------------------------


                                       9


                                  EXHIBIT INDEX


EXHIBIT     DOCUMENT
-------     --------

   1        Joint Filing Agreement by and among the Reporting Persons, dated
            June 22, 2007.

   2        Power of Attorney, granted by William C. Morris relating to Schedule
            13D and 13G filings, in favor of Frank J. Nasta, dated February 2,
            1998

   3        Certificate of Seligman Spectrum Focus (Master) Fund, dated June 15,
            2007


                                       10